The second quote gets my vote!

"Age is not a particularly interesting subject. Anyone can get old. All you have to do is live long enough."
-- Groucho Marx

"Sanity is a madness put to good use."
-- George Santayana

"Good teaching is one-fourth preparation and three-fourths theater."
-- Gail Godwin

"He had discovered a great law of human action, without knowing it - namely, that in order to make a man or a boy covet a thing, it is only necessary to make the thing difficult to obtain."
-- Mark Twain